Acoustic reflectometry device in catheters

Abstract

A device and method for verifying the proper position of catheters in the body by means of acoustic reflectometry, the device including a sound source, one or more sound receivers, a tube with compliant walls and open distal end to be introduced through an entrance to a body cavity, the sound source and receiver(s) coupled to the proximal end of the tube, a processor for causing the sound source to generate an acoustic excitation signal, the processor processing the acoustic signals sensed by the sound receiver(s) and generating an approximation of the acoustic impulse response of the tube, and the processor analyzing the acoustic impulse response to determine the position of the tube in the body cavity.

What is claimed is: 
     
       1. A method for use of acoustic reflectometry in nasogastric enteral access devices, the method comprising:
 inserting a distal end of a nasogastric enteral access device through a naris a distance into a body; 
 emitting sound waves from a sound generator into a proximal end of the nasogastric enteral access device; 
 detecting timings of returning acoustic reflections with at least one sound receiver, the acoustic reflections including an acoustic reflection of a deformation in a wall of the nasogastric enteral access device from an esophageal sphincter; and 
 using a reflectometry device having at least one processor and a memory that is accessible to the processor for analyzing timings of the returning acoustic reflections, including the acoustic reflection from the deformation in the wall, to determine the distance the distal end of the nasogastric enteral access device is inserted into the body. 
 
     
     
       2. The method of  claim 1 , further comprising:
 determining a length of the nasogastric enteral access device. 
 
     
     
       3. The method of  claim 2 , wherein determining the distance the distal end of the nasogastric enteral access device is inserted into the body is based on the determined length of the nasogastric enteral access device and the timing of the acoustic reflection. 
     
     
       4. The method of  claim 3 , wherein the esophageal sphincter is the lower esophageal sphincter. 
     
     
       5. The method of  claim 3 , wherein the esophageal sphincter is the upper esophageal sphincter. 
     
     
       6. The method of  claim 1 , further comprising:
 detecting amplitudes of the returning acoustic reflections with the at least one sound receiver over a time period; and 
 detecting a base and dynamic component of the amplitude over the time period. 
 
     
     
       7. The method of  claim 6 , wherein the dynamic component coincides with a respiratory cycle of the patient. 
     
     
       8. The method of  claim 1 , further comprising:
 clearing the nasogastric enteral access device by providing positive pressure into the nasogastric enteral access device to push fluids out the distal end of the nasogastric enteral access device. 
 
     
     
       9. A method for use of acoustic reflectometry in nasogastric enteral access devices, the method comprising:
 inserting a distal end of a nasogastric enteral access device through a naris a distance into a body; 
 emitting sound waves from a sound generator into a proximal end of the nasogastric enteral access device; 
 detecting, at the proximal end, amplitudes and timings of returning acoustic reflections, with at least one sound receiver, at a plurality of positions of the distal end of the nasogastric enteral access device within the body; 
 using a reflectometry device having at least one processor and a memory that is accessible to the processor for analyzing amplitudes and timings of the returning acoustic reflections to detect a positive amplitude deflection in the acoustic reflections at a first position of the distal end of the nasogastric enteral access device within the body, the positive amplitude deflection in the acoustic reflections being from the distal end of the nasogastric enteral access device; and 
 indicating, based on the detection of the positive amplitude deflection in the acoustic reflections at the first position, that the distal end of the nasogastric enteral access device is above or at the lower esophageal sphincter. 
 
     
     
       10. The method of  claim 9 , further comprising:
 using the reflectometry device having the at least one processor and the memory that is accessible to the processor for analyzing amplitudes and timings of the returning acoustic reflections to detect a negative amplitude deflection in the acoustic reflections at a second position of the distal end of the nasogastric enteral access device within the body, the second position being further advanced into the body as compared to the first position and the negative amplitude deflection in the acoustic reflections being from the distal end of the nasogastric enteral access device. 
 
     
     
       11. The method of  claim 10 , further comprising:
 indicating, based on the detection of a positive amplitude deflection at the first position and the negative amplitude deflection at the second position, that the distal end of the nasogastric enteral access device is within a stomach. 
 
     
     
       12. The method of  claim 9 , wherein the detecting occurs as the distal end of the nasogastric enteral access device is advancing in the body. 
     
     
       13. The method of  claim 9 , wherein the detecting occurs while the distal end of the nasogastric enteral access device is stationary within the body. 
     
     
       14. A system for use of acoustic reflectometry in nasogastric enteral access devices, the system comprising:
 a nasogastric enteral access device; 
 a sound generator to emit sound into the nasogastric enteral access device; 
 at least one sound receiver to detect amplitudes and timings of returning acoustic reflections at a plurality of positions of a distal end of the nasogastric enteral access device within a body; and 
 a reflectometry device having at least one processor and a memory that is accessible to the processor configured to:
 analyze amplitudes and timings of the returning acoustic reflections and to detect a positive amplitude deflection in the acoustic reflections at a first position of the distal end of the nasogastric enteral access device within the body, the positive amplitude deflection in the acoustic reflections being from the distal end of the nasogastric enteral access device; and 
 indicate, based on the detection of the positive amplitude deflection in the acoustic reflections at the first position of the distal end of the nasogastric enteral access device within the body, that the distal end of the nasogastric enteral access device is above or at the lower esophageal sphincter. 
 
 
     
     
       15. A system for use of acoustic reflectometry in nasogastric enteral access devices, the system comprising:
 a nasogastric enteral access device having a proximal end and a distal end; 
 a sound generator to emit sound waves into the nasogastric enteral access device; 
 at least one sound receiver to detect amplitudes and timings of returning acoustic reflections a plurality of positions of the distal end of the nasogastric enteral access device within a body; and 
 a reflectometry device having at least one processor and a memory that is accessible to the processor for:
 analyzing amplitudes and timings of the returning acoustic reflections to detect a negative amplitude deflection in the acoustic reflections at a first position of the distal end of the nasogastric enteral access device within the body, the negative amplitude deflection in the acoustic reflections being from the distal end of the nasogastric enteral access device; and 
 indicating, based on the detection of the negative amplitude deflection in the acoustic reflections at the first position of the distal end of the nasogastric enteral access device within the body, that the distal end of the nasogastric enteral access device is in a stomach.